The present invention relates generally to a system for making and recording light patterns. More particularly, the present invention pertains to a new and improved integrated optic image recorder.
In the field of image recorders, especially laser image recorders, it has been the general practice to utilize a mechanical scanning system to scan a writing laser over the surface to be marked. Marking on the surface is generally accomplished as a result of the sensitivity of the surface to either the heat or light.
Typically the laser is mechanically scanned across the imaging surface. During the scan, it may be modulated to leave a data path of light-struck and non-light-struck areas in each scan. The imaging surface is indexed between scans so that an image is built up on the surface line-by-line. Modulation is typically controlled by voltage pulses from a computer, or the like.
Although excellent results have been achieved by such systems, they require high precision mechanical and optical equipment capable of operating accurately at high speeds. A system for addressing of an imaging surface which avoids the need for high precision and high speed mechanical scanning equipment is desirable.
A variety of approaches to such a system have already been made. For example, the use of a linear array of light emitting diodes is disclosed by James E. Nucklos et al in U.S. Pat. No. 3,803,631 and by E. B. Neitzel in U.S. Pat. No. 3,438,057. Both systems have certain advantages; however, they are both limited by the intensity of the light available from light emitting diodes. Also, the size of commonly available such diodes can frustrate efforts to achieve high resolution patterns.
An imaging system which enables the use of laser light is disclosed by John F. Ebersole in U.S. Pat. No. 3,841,733. Ebersole discloses the coupling of laser light into a waveguide configuration which comprises a parallel array of lithium niobate or tantalate waveguides which are contacted on one side by a common electrode and on the opposite side by individual electrodes.
The lithium niobate or tantalate waveguides of Ebersole propagate TE waves while TM waves are absorbed by the contacting metal electrodes. When attenuation in a particular one of the parallel waveguides is desired, the individual electrode contacting that waveguide is activated. The field between the common electrode and the individual electrode changes the TE orientation of the propagating wave to TM orientation. The TM wave is then absorbed by the metal electrode.
Ebersole discloses the use of such a system to project a line of information on an imaging surface. Each line comprises bits which correspond to individual ones of the waveguides. The bits are illuminated or not depending on whether a field is present across the individual waveguide. Ebersole discloses the use of a high speed buffer interface between the waveguide electrodes and the serial voltage pulses which control the electrodes. The buffer enables line-by-line parallel addressing of the waveguides responsive to serial input.
The waveguide material of Ebersole, is expensive and easily damaged by radiation. A cheaper waveguide made from a material which is less susceptible to radiation damage is desirable.
In the waveguide system of Ebersole, laser light is first coupled into a glass waveguide where it passes through a diverging lens and a collimating lens. Subsequently, the light is coupled into a parallel row of lithium niobate waveguides where it is modulated.
The glass/lithium niobate interface of Ebersole causes reflection problems. An undesirable amount of light is reflected back into the glass from the interface. A waveguide means for producing a line of modulated bits of light while avoiding lithium niobate/glass interface problems is desirable. A convenient method for making such a waveguide means is also desirable.